Checked by Sunni Parks ·
A musty or earthy smell usually traces back to one of three places: the source water itself, a well, or a single faucet — the timing and pattern is what tells them apart.
Causes and what people typically do are based on published guidance from the EPA and state drinking-water programs, not guesses. The zip lookup pulls from EPA's public violation records (SDWIS) and a utility's own water quality report, hand-checked utility by utility rather than scraped.
This tool provides general information based on published EPA and utility data, and common causes reported by water quality professionals. It is not a substitute for laboratory water testing, a licensed plumber's assessment, or guidance from your water utility or local health department. WaterCheck does not guarantee the accuracy, completeness, or timeliness of the information provided and is not liable for decisions made based on it.
Phoenix's own water report names algae in the canals during late summer and fall as a major source of musty or earthy taste and odor. The algae are removed during treatment, but the smell can linger — the city compares it to a room that still smells like flowers after the bouquet is gone. It's an aesthetic issue, not a health one.
About 97–99% of Phoenix's tap water in 2025 was treated surface water from the Salt, Verde and Colorado rivers — Salt and Verde water arrives through the Salt River Project canals, Colorado River water through the Central Arizona Project aqueduct. The remaining ~2% came from about 20 city-operated groundwater wells. Every source is disinfected with chlorine before it reaches your tap.
According to the City of Phoenix's 2025 Water Quality Report, algae that grow in the SRP canals during late summer and fall are a major source of musty taste and odor. Treatment removes the algae, but the odor can linger. The city works to reduce it by removing algae from the canals and using activated carbon at the treatment plants.
Usually, yes — it's typically a smell-only issue caused by natural compounds from algae in a lake or reservoir, organic material in a well, or mold buildup in a single faucet's aerator, not a safety concern.
In warm months, algae in the lake or reservoir that supplies your water gives off natural compounds that smell earthy — the same compounds that make fresh soil smell "earthy." A carbon filter typically clears it up.
That points to mold or mildew built up in that faucet's aerator (the small screen at the tip) or the drain just below it, rather than your water supply. Unscrewing and cleaning or replacing the aerator usually takes care of it.
Organic material — leaves, soil, plant matter — has likely worked its way into the well itself. Having the well "shocked" (a standard cleaning treatment) and checking your filter typically resolves it.